Various types of rod guides and scrapers have been devised to remove wax, paraffin, and other debris from the interior wall of production tubing. Most rod guides include a sleeve-shaped body for positioning over the sucker rod and one or more vanes projecting radially from the body, with one or more vanes being relatively straight (parallel to the axis of the rod), slanted (inclined at an angle relative to the axis of the rod), or helical (spiraling relative to the axis of the rod). The spacing between the vanes, or between a slanted or spiraling single vane, serves as a flow path for passing production fluid past the rod guide.
Most rod guides today are manufactured from a plastic material. Rod guides may be secured in various ways to the sucker rod. In one application, the rod guide is molded onto the sucker rod, and is thus rigid with the sucker rod due to the molding process.
For many applications, a rod guide provided with spiraling vanes is preferred over a straight or slanted vane guide, since more of the circumference of the tubing may be cleaned by a single spiraling guide compared to a single straight-vane guide in a reciprocating rod application. Spiraling rod guides do, however, cause high fluid drag forces to fluid passing by the rod guide and to the surface.
U.S. Pat. No. 5,277,254 discloses a helical rod guide for use with a progressing cavity pump rod. The helical guide may employ either one or two lead vanes. U.S. Pat. No. 6,182,754 discloses a helical scraper for a reciprocating sucker rod. Each of two vanes extends 180°about the body, with the ends of a flow channel between the vanes being parallel to the body of the sucker rod. U.S. Pat. No. 6,439,311 discloses a method of retarding sand buildup by employing helical vanes which are affixed to connective rods by shrink couplings. Other patents of interest include U.S. Pat. Nos. 5,660,534, 5,941,312, 6,065,537, 6,290,475, and 6,484,882, and Canadian Patents 2,260,710 and 2,291,394.
The disadvantages of the prior art are overcome by the present invention, and an improved rod guide and method of molding a rod guide are hereinafter disclosed.